1. Field of the Invention
The present invention relates to a fade detection by which a fade-in or fade-out state of an image is detected based on a video signal.
2. Description of Related Art
A fade detecting apparatus has been known, which uses the video signal itself for the detection of fade-in or fade-out state (hereinafter, referred to simply as a fade state) such that the luminance of a whole image gradually increases or decreases with the lapse of time.
In the fade detecting apparatus, the total luminance value of the video signal corresponding to one frame is compared with the total luminance value of the video signal corresponding to a frame which is one frame before (or after) the above frame. When a difference value between them is kept constant for a predetermined period, a determination is made that the video signal is in the fade state, and a fade detection signal is produced.
In this detecting method, there however is a problem that a real-time operation cannot be made upon detection, and the detecting method cannot be used for a high-speed image processing since the fade state can be determined only after the lapse of the predetermined period as mentioned above.
The invention has been made to solve the problem and it is an object of the invention to provide fade detecting method and apparatus of a video signal, in which a fade state of an image can be detected from the video signal at a high speed.
According to the invention, there is provided a fade detecting method of a video signal for detecting a fade-in or fade-out state of an image from an original video signal constituted by a series of pixel data corresponding to pixels of a picture, comprising: a first fade discriminating step of obtaining, as a first difference absolute value, an absolute value of a difference between the total luminance value of the original video signal of one frame and the total luminance value of neighboring video signal of one frame which are neighboring just before or just after the original video signal, and discriminating whether the first difference absolute value is larger than a first predetermined value or not; a second fade discriminating step of obtaining, as a second difference absolute value, an absolute value of a difference between each pixel data in the original video signal of one frame and each pixel data in the neighboring video signal with respect to pixels existing at a spatially same position, and discriminating whether the number of pixels in which the second difference absolute value is smaller than a second predetermined value is larger than a predetermined number or not; and a fade detecting step of determining that the fade-in or fade-out has occurred on the image in the case where it is decided in the first fade discriminating step that the first difference absolute value is larger than the first predetermined value and it is determined in the second fade discriminating step that the number of pixels in which the second difference absolute value is smaller than the second predetermined value is larger than the predetermined number.
According to the invention, there is provided a fade detecting apparatus of a video signal for detecting a fade-in or fade-out state of an image from an original video signal constructed by a series of pixel data corresponding to pixels of a picture, comprising: delay means for delaying the original video signal by one frame period and obtaining a delayed original video signal; first subtracting means for obtaining, as a first difference absolute value, an absolute value of a difference between the total luminance value of the original video signal of one frame and the total luminance value of the delayed original video signal; first comparing means for comparing whether the first difference absolute value is larger than a first predetermined value or not; second subtracting means for obtaining, as a second difference absolute value, an absolute value of a difference between each pixel data in the original video signal of one frame and each pixel data in the delayed original video signal with respect to pixels existing at a spatially same position; second comparing means for detecting that the second difference absolute value is smaller than a second predetermined value; counting means for counting the number of pixels in which it is detected by the second comparing means that the second difference absolute value is smaller than the second predetermined value and obtaining a count value; third comparing means for comparing whether the count value is larger than a predetermined number or not; and means for generating a fade detection signal indicating that the fade-in or fade-out has occurred on the image when it is determined by the first comparing means that the first difference absolute value is larger than the first predetermined value and it is determined by the third comparing means that the count value is larger than the predetermined number.